Overfishing is reducing the effectiveness of seed dispersal by fish in the Brazilian Pantanal, reports Nature. The research suggests that fishing practices can affect forest health.
In the Pantanal, a giant wetland bordering the Amazon rainforest, many fish species feed on fallen fruit during the flood season. As waters recede and fish return to their low water habitats, seeds are dispersed over a large area.
While scientists have long known that fish disperse seeds in the Amazon, the new research examined the importance of seed dispersal by pacu (Piaractus mesopotamicus), a common freshwater fish, for the tucum palm. The study, led by Mauro Galetti of São Paulo State University in Brazil, found that the tucum palm relies almost entirely on pacu services for seed dispersal.
Satellite view of a section of the Pantanal. Image courtesy of DigitalGlobe
“[It is] amazing that for some plant species, pacu appear to be the main dispersers,” Galetti told Nature.
Larger fish appear to disperse more seeds than smaller fish.
The findings hold ecological significance because populations of large paca are declining in the Pantanal due to a fisheries policy that protects pacu under 40 centimeters, but allows fishing of larger individuals.
“Fishery management like this is probably detrimental to forests since large fruit-eating fish are the best dispersers,” Galetti told Nature. “I think the Amazon and African jungles need to be extensively studied for ecosystems like this. Fish seed distribution is probably a lot more common than we realize.”
The research is published in the journal Biotropica.